This is one of the best, friendliest and best run hotels I have stayed in the past years or so (and I am traveling a lot, ~100,000 miles per year). If you are dissatisfied with how the large "luxurious chain" hotels have become, you have to try a hotel like the Saint-Marc. Friendly personnel, who will do anything to make your family happy, extremely well-maintained facilities with a touch of luxury without being lavish, a freshly prepared breakfast, and some personal nice gadgets (e.g. the honesty bar, an afternoon tea/coffee bar with small cakes etc). You can see and feel that the owners have spent a lot of time, love and efforts to develop the concept of this hotel: well done!! Even though many may not be a fan of art deco, anybody will feel comfortable in these beautifully styled rooms with a lot of special features.
The rooms are extremely spacious and clean, not only with respect to Paris standards. I would therefore especially recommend this hotel when traveling with children, as the rooms will provide a lot of space and comfort.
We will definitely come back and stay here when being in Paris.